Most industrial facilities have a heat loss problem they can’t see. Heat is leaving the system continuously through walls, pipes, openings, and idling equipment. Losing heat means losing energy, causing the machines in your process to work harder, raising the ambient temperature, decreasing efficiency and even shortening equipment life span. The solution starts by understanding where heat escapes your system.
The U.S. Department of Energy identifies the major sources of energy loss in fuel-based systems. In this article, we’ll cover each source and explain the most efficient solution to help you solve this problem.
1. Furnace and Heater Walls
Hot surfaces like furnaces, dryers, and heat exchangers continuously lose energy through both radiation and convection. This is sometimes called wall loss or surface loss. Unfortunately, it is present any time the equipment is operating, even when it’s holding temperature between runs.
On it’s own this is not the worst heat loss issue, but when poor or degraded insulation on furnace walls goes unreplaced heat loss increases dramatically.
Per the US Department of Energy, poor insulation conditions are a key source of energy loss and often overlooked during routine maintenance reviews. Furnace walls, connected piping or ductwork are the most common areas for heat loss in this first category.
Fortunately the solution for this category is fairly simple; Regularly replacing insulation with insulation solutions, like those found on shop.unitherm.com, is a simple, cost effective fix.
2. Openings, Doors, and Seals
Every time a furnace door opens, heat escapes by radiation. Even closed doors with gaps and worn seals can allow radiant heat to escape. Radiation heat loss from openings is a specific category of loss which results from not having proper seals at doors used for material handling.
Checking and maintaining door seals regularly is a low-cost maintenance step that can reduce this loss meaningfully.
3. Flue and Exhaust Gases
For fuel-fired systems, exhaust gases carry a large portion of the heat energy out of the system. Flue gas losses are one of the largest sources of energy loss in fuel-based process heating. The higher the exhaust gas temperature, the more energy is being lost.
This is the category that waste heat recovery systems are designed to address — capturing heat from the exhaust stream and putting it back to work, either as preheated combustion air or for other process uses.
4. Piping and Ductwork Without Insulation
Hot piping, ductwork, and valves that run between the heating source and the process lose heat at every uninsulated foot. This is especially relevant in facilities where heated fluids, gases, or steam travel significant distances. Each uninsulated surface is a continuous energy drain.
UniTherm’s IsoCovers are removable insulation covers designed for pipes, valves, and flanges. They’re an effective, convenient, and low-cost way to address heat loss on piping components — and because they’re removable, they don’t interfere with maintenance access. Learn more at unitherm.com/pipe-and-components.
5. Idle and Low-Capacity Operation
Process heating systems have both fixed and variable losses. Variable losses depend on how much material is being heated. Fixed losses occur as long as the unit is operating, regardless of capacity. When a furnace sits idle between batches or runs at low capacity for extended periods, those fixed losses — wall heat, exhaust gases, radiation — continue accumulating without productive output to offset them.
Scheduling improvements that reduce idle time are one of the enabling technologies the DOE sourcebook identifies for improving overall system efficiency.
Where to Start
Not every facility has the same loss profile, and not every improvement requires capital investment. A walk-through of your system with attention to surface temperatures, insulation condition, and door or seal integrity can reveal opportunities quickly. If pipes, valves, or equipment surfaces are hot to the touch — or hot enough to be uncomfortable to stand near — that heat is money leaving your process.
For our standard removable insulation solutions, visit shop.unitherm.com.
To request a quote for a custom insulation solutions click here.
Source: U.S. DOE, Improving Process Heating System Performance: A Sourcebook for Industry (Third Edition), 2015.